Field of the Invention
The present invention relaters to an automatic hand tool, in particular to a pneumatic tool capable of driving knifes to be moved reciprocately.
Description of the Prior Art
As shown in FIGS. 7 and 8, a conventional pneumatic saw driving structure is illustrated. A driving gear 92 is assembled in the pneumatic saw 91, and an eccentric post 93 is assembled on the driving gear 92. A transmission block 95 is fixedly assembled at an end portion of a saw plate unit 94. The transmission block 95 has an elongate slot 951, and the eccentric post 93 can be slidably abutted against the elongate slot 951. When the driving gear 92 is rotated, the eccentric post 93 pushes the transmission block 95 to move along the elongate slot 951, so that the saw plate unit 94 can perform a reciprocate motion in a linear housing.
However, in such mechanism, the elongate slot 951 needs to have a space for sliding the eccentric post 93. Therefore, a gap 96 is formed between the eccentric post 93 and the elongate slot 951. In other words, in such mechanism, the transmission block 95 at the end portion of the saw plate unit 94 is not fixed with the eccentric post 93 and can be slid relative to the eccentric post 93. As a result, when the saw plate unit 94 performs a fast reciprocate motion, the saw plate unit 94 is not steadily positioned and may deflected easily, resulting the wearing of the components and the noise issue.